Broken circle on Link belt stroker

[larslog]

Company I work for bought a 1998 Link Belt 3400 Quantum with a Pierce stroker 2 years ago that was cracked out around where the upper bolts to the Rotec circle bearing.They had a local machine shop weld it but since then it has broken out twice more.Is this common on these and is it something that can be fixed permanently?This machine has the highwalker undercarriage(4300 size??) on it.

 

[Chipensaw]

Yes, very common on the Q series. Two much flex in the upper structure floor where the circle bolts on. The machine needs to be split again, welded up and reinforced inside to limit the flex that occurs.

JR

 

[tree farmer]

Linkbelt 3400Q

After the upper deck is reinforced, the bolt circle area where the rotec fastens should be checked for warps. I have heard of this surface and the other bolt surface on the carrier being remachined (ground) to flat surfaces. Lineborer posted a link to some handy tools in one of the threads. I don't know if they have the proper device for this job.

 

[larslog]

Thanks for the information.Do you know how it should be reinforced?Should the deck floor be plated or braces from the frame welded to the floor or both be done?Also how critical is it that the surfaces be machined as I don't think they plan on splitting it,just welding it from on top.Trying to fix it on the cheap. Thanks again

 

[tree farmer]

Thanks for the information.Do you know how it should be reinforced?Should the deck floor be plated or braces from the frame welded to the floor or both be done?Also how critical is it that the surfaces be machined as I don't think they plan on splitting it,just welding it from on top.Trying to fix it on the cheap. Thanks again

Any warps in the bolt surface will reduce the life of the rotec bearing. The cracks that will be welded will never totally go away. Steel being a crystalline structure will harbor the "seed" of the crack. New metal deposited will adopt the same pattern unless you V the crack to within 1/8 inch of the bottom of the crack formation. The first weld pass will need to be hot enough to burn clear through and melt away the old metal with the crack in it.
For example a forklift tooth with a crack can be fixed by Ving out the crack until there is a silver of steel with the crack still holding the tooth together. The first weld pass will burn clear through melting the old ruptured crystal structure and leaving fresh new metal. Fill the V with good welding and you have a tooth as good as new.
The fish plating and bracing you will be adding should supplement and help hold the crack areas closed. Reducing the flexing of the upper body will help slow down the crack from reforming. Drilling a hole just in advance of a crack forming on plate steel will often eliminate the crack "seed" and stop the pattern. A good welder will know how to spread the weld around equally thus causing less warping.